CHILD LANGUAGE Acquisition of speech sounds, segmenting the phonetic string The target • Arbitrary relationship between sound and meaning • Abstract concepts, displacement from here and now • Hierarchical organisation, compositionality: sounds-words-(phrases)-clauses-sentencestext • Astronomical (perhaps infinite) number of form-meaning pairings The target • Sketchiness: only some of the intended meaning is expressed explicitly, the rest has to be inferred by the listener – Done. • Ambiguity: words, structures, whole sentences may be ambiguous – relevant meaning needs to be recovered from context – Drunk gets nine months in violin case (Pinker 1984) • Cultural embeddedness: communication requires implicit understanding of the intentions of conversation partners, social habits – She had her leg waxed vs. She had her leg broken • Transmissibility: messages are transmitted rapidly and relatively errorlessly – processing is done on-line using a variety of sources of information The input • • • • Varies across cultures No systematic instruction in most cultures Teaching at best through correction of errors Syntactic rules are never explained, most people are not aware of them Speech sounds • Set of acoustic cues identify speech sounds • They are influenced by: – Neighbouring sounds – Overall utterance prosody – Speech rate – Speaker voice quality – Environmental noise, etc. Phonemes and allophones • Phoneme: speech sounds that distinguish words (sinner vs. singer) • Allophones: phonetically different speech sounds that do not distinguish words (enged) • Every language has its own phoneme inventory • Categorical perception: we cannot hear “meaningless” differences in sounds. Sounds are automatically categorised. 19th century Headturn preference • • • • Head-turn preference paradigm Light from left or right Auditory stimulus from same area Length of looking measured Results of experiments: language discrimination • Newborns can distinguish their native language from other languages of a different rhythm (Mehler et al 1988) • They can also discriminate between two unfamiliar languages of different rhythms (Mehler & Christophe 1998, Nazzi et al 1998) • But at 2 months of age they stop discriminating between unfamiliar languages (Mehler et al 1988, Christophe & Morton 1998) • In the first few months discrimination is based on rhythm and intonation • At 5 months, infants can also rely on individual speech sounds (they can distinguish languages with similar intonation patterns, such as Dutch and English) (Nazzi et al 2000) • By 9 months, infants prefer to listen to unknown words not violating the phonotactic patterns of their language (e.g., pottle vs. tlepen) • They also prefer nonsense words with frequent sound combinations Results of experiments: phoneme discrimination • Categorical perception at 1 month of age (Eimas 1975) • Confirmed by ERP studies: odd-ball detection paradigm (electrophysical response to novel auditory stimulus) (Cheour-Luhtanen et al 1995) • For the first few months, infants can distinguish phonemes in any language, but by age 6-8 months, they are only sensitive to contrasts in their native language (Kuhl et al 2006) • At 9 months, infants can re-learn to discriminate phonemic contrasts in foreign languages (Kuhl et al 2003) – after twelve 25 minute reading sessions Kuhl: The linguistic genious of babies http://www.youtube.com/watch?v=G2XBIkHW954 Possible learning mechanisms • Top-down from word meaning: phonemes distinguish words – But 10 month-olds have a very small vocabulary • Distributional learning: – non-contrastive sound pairs (allophones) occur in complementary distribution – e.g. English vowel nasalisation – systematic phonetic variation which is not contextually predictable is contrastive in the target language • Categories influence perception: items in the same category are perceived to be more similar than items across category boundaries Segmentation • There are no universal syllables • Languages differ widely in their rhythmic structure • Only subtle cues to word boundaries (segment duration, allophonic variation, phonotactics), but they are neither obvious nor universal • Segmentation errors are common in adult speech processing • Top-down processes seem to play a major role for adults whereare the s Saffran 2003 ilen ces betw eenwor d s Distributional evidence • Transitional probabilities • pretty baby, pretty dress, pretty doll -> pre+ty highly probable (within word), ty+ba less probable (across word boundaries) • Nonsense language learning experiments (Saffran et al 1996, Aslin, Saffran & Newport, 1998): In training phase 8 month-olds listen to uninterrupted sequence of 3syllable words: bidakupadotigolabubidaku In test phase they listen longer to nonwords (kupado) than to words (bidaku) • Works with musical notes (Saffran, Johnson, Aslin & Newport 1999) • Tamarin monkeys are as sensitive as human children (Hauser, Newport & Aslin, 2001) • Infants under 6 months cannot reliably identify these word segments Statistical learning • Implicit, procedural learning of probabilistic co-occurrence patterns • based on invariance detection through attention to relatively stable patterns or regularities (Gogate & Hollich 2010) Prosodic properties as cues • Noise detection experiments 6 month-olds are slower to detect noise if it interrupts two-syllable sequences with typical stress pattern (Morgan 1996) • 9 month-olds prefer words with typical stress pattern (Jusczyk 1997, 1999, 2002) • they listened to isolated words with typical (kingdom, hamlet) vs. atypical (device, align) stress pattern • then they listened to passages with or without the test words • they listened longer to passages with the typical words • Frequency of sounds varies by environment: word initial, word medial, across word boundaries. 9 month-olds are sensitive to these patterns (Mattys & Jusczyk 2001, Brent & Cartwright 1996)